dansup, I've been talking about this exact thing for at least a year. Like, "I would like to know in advance whether this object supports this activity". This would also make sense to combine with privacy settings, as in, "you can send this activity but only if this actor follows you".

@dansup the standard way to discover capabilities will eventually be much needed.

But I'm interested in what comes before: the ease-of-development of entirely new application types that are not silo's afterwards, but rather building-blocks for a more task-oriented fedi.

Here thinking that AP vocab extensions represent the domain structure found by DDD and messages represent some of the events from the domain-driven design (event storming) as they travel the network. AP is wire protocol here.